1. Field of the Invention
The present invention relates to a method of preparing a radioisotope nanostructure having a ligand-metal framework, and an application thereof.
2. Description of the Related Art
Isotopes having radioactivity are referred to as radioisotopes (RI). About 300 species of natural isotopes include about 40 species of radioisotopes, most of which are isotopes of elements having atomic numbers larger than thallium. Recently, in addition to the natural radioisotopes, about 1000 species of artificial radioisotopes have been prepared, which are distributed using almost all elements. Typically, artificial radioisotopes are made by irradiating stable elements or compounds with a nuclear reactor or a particle accelerator, and are widely utilized in tracing movement of elements or compounds in materials or living bodies, investigating radiation effects on materials or organisms, serving as industrial or measuring radiation sources, performing analysis of materials using radioactivity, etc. Among these, a radioisotope used to trace the movement of elements or compounds is referred to as a radioisotope tracer. Radioisotope tracer techniques are used to achieve high-grade analysis of industrial processing related to refineries, chemistry, cement, etc., and can also lead to technological breakthroughs in the areas of the environment, medicine, agriculture, resource exploration, etc.
In order to effectively use such radioisotope tracer techniques, preparation of a radioisotope tracer is regarded as very important. Although there are slight differences depending on the application field, radioisotope tracers are required to have properties in which nuclei themselves may emit radiation and are thus converted into other kinds of nuclei, without being affected by external environments, such as pressure, temperature, chemical treatment, etc. Furthermore, in order to apply radioisotope tracers to high-temperature and/or high-pressure fluids, the tracer has to be chemically and physically stable, and should also have a density similar to that of a fluid and may thus be provided in the form of a mixture with the fluid. Typical radioisotopes, such as 198Au, 63Ni, 108Ag, 64Cu, 60Co, and so on are metals and have very high density and specific gravity compared to those of fluid media, and cannot be used in fluids for the diagnosis of industrial processing. Thus, a variety of attempts are being made to apply the radioisotope tracers to high-temperature and/or high-pressure fluids.
Korean Patent No. 10-1091416 discloses a core-shell nanostructure which is nano-sized and emits gamma rays while being stable at high temperature and high pressure, and also two-nuclide core-shell nanostructures are disclosed (J.-H. Jung, et al., Applied Radiation and Isotopes, (2012), in press). However, the core-shell nanostructures are problematic because a plurality of steps including preparation of nanoparticles, silica coating, organic treatment, neutron irradiation, and so on should be conducted, undesirably causing complicated preparation processes, and also because a long period of time is required to separate the nanoparticles from the silica coating solution using centrifugation, undesirably making it difficult to accomplish mass synthesis.
Meanwhile, a radioisotope 68Ga3+ cation has been used as a radioisotope tracer for PET imaging by subjecting the cation to complexation with a ligand such as DOTA, NOTA, and the like and then binding the complex to a protein (E. Boros, et al., J. Am. Chem. Soc., (2010) 132: 15726-15733). However, in the case of the above ligand, coordination polymerization cannot be performed, making it impossible to prepare a spherical nanostructure suitable for high-temperature and high-pressure industrial processing environments.
As mentioned above, to effectively apply the radioisotope tracer techniques to high-temperature and high-pressure industrial processing environments, development of alternative techniques for preparing a radioisotope tracer which is physically and chemically stable and is easy to form thus enabling mass production is required.